Catalyst regeneration



Sept. 15, 1959 CQRNFIELD ETAL 2,904,519

CATALYST REGENERATION Filed Oct. 14, 1953 A z A 4.21%.}...

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D LN EE IT M T m m CN I mm Mm DE EB mm EL m S F AL ATTORNEYS UnitedStates Patent CATALYST REGENERATION Albert Edward Cornfield and LeslieBenjamin Witten,

Suubury-on-Thames, England, assignors to The British Petroleum CompanyLimited Application October 14, 1953, Serial No. 385,922

Claims priority, application Great Britain October 17, 1952 4 Claims.(Cl. 252-420) This invention relates to catalytic processes usingcatalysts containing aluminum and fluorine.

For example, in the so-called autofining process for the hydrocatalyticdesulphurisation of petroleum hydrocarbons catalysts may be usedcomprising a minor amount of fluorine within the range 0.1 to 6.0% wt.,and the oxides of cobalt and molybdenum supported on activated aluminaall as described in the specification of co-pending United Statesapplication Ser. No. 311,429, filed September 25, 1952, now Patent No.2,800,429. Presumably, even probably, but not inevitably, the aluminiumand fluorine are present as aluminium fluoride. It has been found,however, that such fluorinated catalysts tend to lose fluorine duringthe regeneration of the catalyst when it is subjected to temperatures ofthe order of 1100 F. in the presence of steam.

It is known that the so-called carbonaceous deposit formed on catalystsduring the hydrocatalytic desulphurisation process consists in fact ofhigh-boiling hydrocarbons. The purpose of the regeneration step is toburn off these hydrocarbons which impair the activity of the catalyst.Such regeneration may be eflected by heating the catalyst at an elevatedtemperature with steam and air, in which case steam is obviouslypresent. Alternatively, regeneration may be etfected by inert gas andair at elevated temperature, but in this case steam is also presentsince on combustion the hydrocarbonaceous deposit yields steam andcarbon dioxide. Either method of regeneration involved the presence ofsteam.

It is an observed fact that during regeneration, the temperature ofwhich is determined by the necessity to burn off the hydrocarbonaceousdeposit, hydrogen fluoride is evolved and is found in the regenerationgases. The precise mechanism by which the hydrogen fluoride is formed isnot known, but assuming that the aluminium and fluorine are present asaluminium fluoride the steam probably reacts with the aluminium fluorideto form hydrogen fluoride. It is known that hydrolysis of aluminiumfluoride takes place at the regeneration temperature. It is believedthat such loss of fluon'ne is due to the hydrolysis of the aluminiumfluoride in the catalyst by the steam, the resulting hydrogen fluoridebeing carried away with the the regeneration gases.

A process has now been developed for the regeneration of catalystscontaining aluminium and fluorine by means of which this loss offluorine arising when the catalyst inevitably though undesirably comesinto contact with gases containing steam, may be substantially reduced.

According to the invention, in a process for the regeneration of acatalyst containing aluminium and fluon'ne in which the catalyst comesinto contact with gases containing steam at a temperature at whichaluminium fluoride is hydrolysed with the formation of hydrogenfluoride, the exit gases from each regeneration are passed over acatalyst mass containing aluminium but containing no fluorine or havinga fluorine content below the desired content in the catalyst, at atemperature low enough to cause the hydrogen fluoride in theregeneration gases ICC to be taken up by the catalyst mass, until thefluorine content of the catalyst mass has reached a value at which thecatalyst mass is satisfactory for use in the catalytic process.

By operating the catalytic process with a plurality of reactors, one ofwhich is always in use for the recovery of hydrogen fluoride from theregeneration gases, it is possi ble to operate the catalytic processcontinuously with the minimum loss of fluorine.

The exit gases from the regeneration stage are advantageously cooled toa temperature of between 200 and 700 F. before being passed over thecatalyst mass.

The application of the process of the invention to the autofiningprocess will now be described with reference to the accompanying flowdiagram.

The system illustrated comprises three reactors A, B and C. At the startof the process, reactors A and B contain catalyst containing aluminiumand fluorine and reactor C contains a similar catalyst having nofluorine or a fluorine content below the desired content in thecatalyst. Reactors A and B are used alternately for processing thefeedstock and when each is being regenerated the exit gases are cooledto a temperature of between 200 and 700 F. and passed to the reactor Cwhere the hydrogen fluoride in the regeneration gases is taken up by thefluorine-deficient catalyst. This process is continued until the meanfluorine content of the catalyst in the reactor C has reached the upperlimit to an amount of fluorine desired in the catalyst or the meanfluorine content of the catalyst in either of the reactors A and B hasreached the lower limit to an amount of fluorine desired in thecatalyst, whereupon the reactor C is brought on-stream and either of theon-stream reactors A and B after regeneration, is used for the recoveryof fluorine as described with respect to reactor C.

The process and regeneration systems are of conventional arrangement.Thus the feedstock to be treated is fed from tank 10, by means of pump11 to heater 12 from which it passes toreactor A. The products fromreactor A are passed through cooler 13 to a high pressure separator 14from which liquid product containing hydrogen sulphide in solution isremoved via line 15. A hydrogen-rich gas is removed from the separator14 via line 16 and recycled by means of gas booster 17 into admixturewith the fresh feed, any excess gas being withdrawn via line 18.

During regeneration, air is admitted via line '19 and inert gas via line20, and the mixture of air and inert gas is passed through heater 21 andthence through reactor B containing the catalyst mass to be regenerated.Since the so-called cabonaceous deposit which is formed on the catalystduring the hydrocatalytic desulphurisation process and which is to beremoved, consists in fact of high boiling hydrocarbons, the temperatureof the mixture of air and inert gas entering the reactor B has to besufliciently high to burn ofl? these hydrocarbons which impair theactivity of the catalyst. On combustion, the hydrocarbonaceous deposityields steam and carbon dioxide. At the regencration temperature,hydrolysis of the aluminium fluoride takes place with the formation ofhydrogen fluoride. The gases leaving reactor B and containing anyhydrogen fluoride formed by hydrolysis of the aluminium fluoride in thecatalyst are passed through cooler 22 to reactor C and thence Via line23 to Vent. If desired, part or all of the gases from line 23 may berecycled to the reactor B by means of gas booster 24 and line 25.

Any overall loss of fluorine from the system may be made up by any ofthe methods described in the specifications of the co-pending Britishapplication No. 30049/52, now Patent No. 747,663.

We claim:

1. In a process for the regeneration of a catalyst comprising oxides ofcobalt and molybdenum supported upon alumina and containing a minoramount of fluorine withinthe range 0.1 to 6.0% wt., in which process thecatalyst comes into contact with steam in a regeneration stage, at asuitable regeneration temperature above 700 F., and hydrogen fluoride isformed, and in which the hydrogen fluoride formed is carried away in theexit gases from said stage, the steps comprising passing the exit gasesfrom the regeneration stage while they still contain the hydrogenfluoride, over a catalyst mass comprising oxides of cobalt andmolybdenum supported upon alumina but containing no fluorine, at atemperature of between 200 .and 700 F. to cause the hydrogen fluoride insaid gases to be taken up by the catalyst mass, and continuing thepassage of said gases until the fluorine content of the catalyst masshas reached said minoramount.

2. In a process for the regeneration of a catalyst comprising oxides ofcobalt and molybdenum supported upon alumina and containing a minoramount of fluorine within the range 0.1 to 6.0% wt., in which processthe catalyst comes into contact with steam in a regeneration stage, at asuitable regeneration temperature above 700 F., and hydrogen fluoride.is formed, and in which the hydrogen-fluoride formed iscarried away inthe exit gases from said stage, the steps comprising passing the exitgaseslfrom the regenerationstage while they still contain the hydrogenfluoride, over a catalyst mass comprising oxides of cobalt andmolybdenum supported upon alumina but containing an amount of fluorine,if any, less than said minor amount, at a temperature of between 200 and700 -F. to cause hydrogen fluoride in said gases to be taken up by thecatalyst mass, and continuing the passage of said gases until thefluorine content of the catalyst mass has reached said minor amount.

3. In aprocess for the regeneration of a catalyst comprising oxides ofcobalt and molybdenum supported upon alumina and containing a minoramount of fluorine within the range 0.1 to 6.0% wt., in which thecatalyst comes into contact with steam-in a regeneration stage, at asuitable regeneration temperature above 700 F., and

hydrogen fluoride is formed, and in which the hydrogen fluoride formedis carried away in the exit gases from said stage, the steps comprisingcooling the exit gases from the regeneration stage to a temperature ofbetween 200 and 700 F., passing the cooled gases at said temperature andwhile they still contain the hydrogen fluoride, over a catalyst masscomprising oxides of cobalt and molybdenumsupported upon alumina but.containing no fluorine, so that hydrogen fluoride in the regenerationgases is taken up by the catalyst mass, and continuing the passage ofsaid gases until the fluorine content of the catalyst mass has reachedsaid minor amount.

4. In aprocess for the regeneration of a catalyst comprising oxides ofcobalt and molybdenum supported upon alumina and containing a minoramount of fluorine within the range 0.1 to 6.0% wt., in which thecatalyst comes into contact with steam in a regeneration stage, at asuitable regeneration temperature above 700 F., and hydrogen fluoride isformed, and in which the hydrogen fluoride formed is carried away in theexit gases from said stage, the steps comprising cooling the exit gasesfrom the regeneration stage to a temperature of between 200 and 700 -F.,passing the cooled gases at said temperature and while they stillcontain the hydrogen fluoride, over a catalyst mass comprising oxides ofcobalt and molybdenum supported upon alumina 'but containing an amountof fluorine, if any, less than said minor amount, so that the hydrogenfluoride in the cooled gases is taken up by the catalyst mass, andcontinuing the passage of said gases until the fluorine content of thecatalyst mass has reached said minor amount.

References Cited in the file of this patent UNITED STATES PATENTS2,031,600 Harrison et a1. Feb. 25, 1936 2,339,685 De Simo et al Jan. 18,1944 2,487,466 Nahin Nov. 8, 1949 2,487,717 Maker et a1. Nov. 8, 19492,551,145 Loy May 1, 1951 2,580,004 Corneil -Dec. 25, 1951 2,642,384 CoxJune 16, 1953

1. IN A PROCESS FOR THE REGENERATION OF A CATALYST COMPRISING OXIDES OFCOBALT AND MOLYBDENUM SUPPORTED UPON ALUMINA AND CONTAINING A MINORAMOUNT OF FLUORINE WITHIN THE RANGE 0.1 TO 6.0% WT., IN WHICH PROCESSTHE CATALYST COMES INTO CONTACT WITH STEAM IN A REGENERATION STAGE, AT ASUITABLE REGENERATION TEMPERATURE ABOVE 700* F., AND HYDROGEN FLUORIDEIS FORMED, AND IN WHICH THE HYDROGEN FLUORIDE FORMED IS CARRIED AWAY INTHE EXIT GASES FROM SAID STAGE, THE STEPS COMPRISING PASSING THE EXITGASES FROM THE REGENERATION STAGE WHILE THEY STILL CONTAIN THE HYDROGENFLUORIDE, OVER A CATALYST MASS COMPRIING OXIDES OF COBALT AND MOLYBDENUMSUPPORTED UPON ALUMINA BUT CONTAINING NO FLUORINE, AT A TEMPERATURE OFBETWEEN 200* AND 700* F. TO CAUSE THE HYDROGEN FLUORIDE IN SAID GASES TOBE TAKEN UP BY THE CATALSYT MASS AND CONTINUING THE PASSAGE OF SAIDGASES UNTIL THE FLUORINE CONTENT OF THE CATALYST MASS HAS REACHED SAIDMINOR AMOUNT.